Method of coating articles with pyroxylin or the like



- form has been entirely lackin Great Patented Oct. 11, 1932 UNlTED' STATES PATENT OFFICE WILLIAM C. HAMPTON AND CHARLES N. GABBEB, 0F DAYTON, OHIOQASSIGNOBS TO THE CRAWFORD, MCGREGOR AN DCANBY COMPANY, OF DAYTON, OHIO, A CORPORATION 01'' OHIO METHOD OF COATING ARTICLES WITH PYROXYLIN OR THE LIKE No Drawing.

This invention relates to a method of coating articles of metal, wood, or other material with a surface covering of celluloid or pyroxylin applied in liquid form and subsequently cured thereon to afford a continuous, onepiece, adherent envelope of substantially uniform thickness of quite considerable depth at a single operation and possessing asmooth and highly polished surface.

While reference is made in some prior patents to proposed applications of ceilulold or pyroxylin as a coating material by dlpping articles in a body of such materials in liquid form, such suggestions have been prophetlc only and the necessary teaching for successful working of pyroxylin materials in li ufiiid culty is encountered in'contro g the material subsequent to the dipping operation and in efi'ecting a curing of the coating material which will leave a finished surface undistorted and unblemished. Many unusual problems have been presentedin effecting a. uniformly smooth polished surface deposit for which the hereinafter stated method aifords a commercially practical solution.

. ing atmosphere upon the coated surface. If

such moisture condensation tricklesin streams upon the newly coated surface, it produces and by un-uniform shinkage of such outer streaks and discoloration as well as distortion and a rough or matte surface.- If such condensation stands in the form of dew, ice crystals, or drops upon the freshly coated surface, it produces .a rough and pitted surface effect. If the outer surface of the deposit is permitted to se too quickly, it forms an impenetrable film which prevents the escape of the solvent from the inner strata surface film upon the inner material while yet in air'soft condition, it induces wrinkling and produces a crinkled surface of intricate design; If the freshly coated body is main- Applfcation fled June 18, 1980. Serial No. 460,786. I

tained at a moderate temperature sufiicient to effect rapid evaporation of the solvent before such surface film can form, the solvent is quite likely to boil or vaporize within the" deposit of coating material, thus forming pimples and bubbles and causing the mate- ,rial toswell or balloon often assuming odd and grotesque shapes. From'the experience of many such failures, the hereinafter method or process of successful treatment of articles by dipping in liqui Pyroxylin or celluloid has been evolved.

The object of the present invention is to provide a comparativel simple, economical, and commercially practical method for covering various articles of wood, metal and other materials, such as steering wheels forautomobiles, door knobs, handles for cutlery, golf clubheads and shafts, bathroom fixtures toilet seats, and numerous other articles of everyday commercial and household use with a covering of celluloid or pyroxylin having a uniformly smooth surface possessing a natural high polish or luster without the necessity o mechanical polishing or finishing operation, and of'increased durability and capable of withstanding hard usage and wear, and which will provide a continuous onepiece cove without seams or joints,-hermetically the enclosed body against entrance of moisture or attack by vapors or the like. 7

'A further object of the invention is to provide an improved method. orrprocess of applying celluloid and pyroxylin in liquid form and controlling the resulting depos1t to prevent watering from rapid evaporation, pitting or eggshell surface effect from dew or ice crystal deposits of moisture condensation, pimpling and bubble formation as re-' sult of boiling or vaporization of the contained solvent, and wrinkling or orange peel efl'ect due to un-uniform :1

A further object of the invention is th rovide a method and process by which various articles may be coated 'with celluloid or pyroxylin of various colors, giving to the ar ticles pleasing and ornamental color effects.

A further object of the invention is to provide a method or process of enpasing artlcleswithin a covering of celluloid or pyroxylin of greater or less thickness, the extent of which may be controlled at will,'and which may be deposited many times deeper than that of other finishing materials such as paints, lacquers, and varnishes, encasements having thickness of from twenty to sixty thousandths of an inch being ordinarily produced at a single dipping operation.

A further object of the invention is to provide a protective coating upon articles of wood, metal, and other material which will be tightly adherent, forming substantially a homogeneous body but which will at the same time possess sufficient flexibility to prevent cracking, chipping, -crazing, and fracture.

A further object of the invention is to provide a coating or covering material which, when applied to articles possessinga degree of flexibility or resiliency such as shafts of golf clubs, canes, umbrella handles and the like, will yield in unison with the coated article.

With the above primary and other incidental objects in view, as will more fully appear in the specification, the invention consists of the steps and procedure, the apparatus and the method of operation or their equivalents as hereinafter described and set forth in the claims.

In carrying out the present process, any suitable solvent for pyroxylin or for celluloid such as ether, alcohol, acetate, or the like,

may be employed. However, acetone is the best known and preferable solvent for this purpose. The process consists of three major operations, to wit, first the preparation and application of a rather thick, viscous solution of pyroxylin, second, the extraction of a considerable portion of the solvent by chemical or other means as by plunging the coated article into a bath of liquid having-a great affinity for the pyroxylin solvent and third, the evaporation of the remaining solventby governing such evaporation by temperature control and by preconditioning the air in which the curing of the material is effected.

Preparatory to the dipping or coating operation, the pyroxylin or celluloid, as the case may be, is thoroughly dissolved in a suitable solvent until the material becomes a viscous, heavy liquid. This mixture of the material and the initial coating or dipping operation are best and preferably performed in a room of normal temperature of approximately seventy degrees Fahrenheit. The

viscous dipping solution takes approximately the same temperature or one somewhat lower due to the refrigerating. effect of the evaporation of the solvent. The coating liquid .is of much thicker consistency than ordinary paint or lacquer, and therefore a quite heavy coating or deposit upon the article is obtainable.

After the article to be coated has been dipped into the liquid pyroxylin or celluloid i,se2,574

or immersed in a bath of liquid which has an 3 afiinity for the pyroxylin solvent, and which is maintained at a comparatively low temperature, preferably a temperature below zero Fahrenheit. Y

The liquid coating material is very sensitive to temperature change, and when chilled becomes set into a semi-solid form in which the tendency to flow or change its shape is greatly retarded if not entirely overcome. Therefore the low temperature of the plunge bath has the effect of solidifying the coating material upon the article to such extent that it will maintain its shape and will overcome any tendency to flow or distort.

The liquid bath in which the coated article is immersed is preferably one having a great afiinity for the pyroxylin solvent in which the solvent will readily mix or dissolve but in which the pyroxylin itself is insoluble. Such liquids as gasoline, benzine, benzol and the like, have been found quite practical in carrying out the present method. Such liquids while having a strong tendency to attract or dissolve the acetone or other solvents employed do not dissolve the cellulose, pyroxylin or celluloid to any appreciable extent,

i. e., gasoline, benzene and benzol may have a tendency to dissolve out the camphor contained in the celluloid or pyroxylin inthe event that the work is left immersed too long in the bath. In the short time ordinarily required to set the coating material and to extract the solvent this effect upon the camphor content isnegligible. However, under conditions where it may be found necemary to immerse the coated article for a lon r riod of time, the action of such bath quid may be compensated for by adding a little excess camphor-to the composition. i

In lieu of maintaining the solvent extracting bath at an extremely low temperature, separate baths may be employed, one of which is a; setting bath maintained at low temperature for solidifying the coating ma-- terial andfrom which the coated article is transferred to a difleren bath at somewhat higher temperature by w 'ch the solvent is extracted but always maintained below the vaporization or boiling point'of the solvent. The first or setting bath need not necessarily benzol, benzine, gasoline or the like in which the solvent is soluble andwhich has a great.

affinity for the solvent and so while solidify ing the coating it also serves to extract some of the solvent thusaccelerating the setting or hardenin of the material and preventing distortion. xtraction of solvent will, however, progress very slowly at such low temperature. At such temperature the bath has little or no effect on the camphor content.

After being left in the initial bath sufficient time to become thoroughly chilled,

.which ordinarily requires from ten to fifteen minutes, the article is transferred to a second bath of benzol, benzine, 88011118 or other non-freezing material having great aflimty for the solvent, which is maintained at a somewhat higher temperature of approximately zero Fahrenheit, by which the extrac tion of the solv'entis effected at a more rapid -rate,-and which results in further hardenm and solidification of the coating materia When the greater portion of free solvent has been removed and the action of the bath has diminished, the article may, if desired, be

transferred to a third similar bath at a still higher temperature of approximately forty degrees Fahrenheit for the extraction of remaining1 ing to-t 0 size of the article and thickness of the coating. In practice, however, it is found that such third bath is but seldom necessary.

The difficulties ordinarily encountered due to the too rapid evaporation of the solvent and deterioration and distortion of the coating material such as wrinkling, pimpling, and blushing or watering causing discoloration due to the refrigerating effect of the rapid 'evaporation; are overcome by the immersing of the coated article in this cold solvent-extracting bath. The low temperature of the bath changes the viscosity of the coating material so greatly that it becomes set'almostimmediately, and the absorption or extraction of the solvent further increases the setting or hardening of the deposited pyroxylin material. However, this hardening or setting of the material is effected in the bath without the formation of an impervious surface film which would tend to prevent the escape of any remaining solvent and result in wrinkling or pimpling. To the contrary upon removal from the bath, any remaining solvent may be freely evaporated during the subsequent curing operation.

solvent, the period varying accord After removal. from the liquid bath, the coated article is dried in a cold room from the air of which the moisture has been extracted to a point of low humidity so that the refri rating effect of the evaporation of any remaining solvent which tends to lower the temperature of the work will not cause moisture condensation. The drying or curing is preferably effected at a quite low temperature. A temperature of below zero Fahren heit is ordinarilfy employed, and a temperature as low as rom twenty to fifty degrees Fahrenheit below zero has-been found to be quitesuccessful and practical. The work is maintained at-low curing temperature until 80 substantially all of the solvent has been evaporated, thereby avoiding danger of n wrinklin pimpling or blistering due to the too rapi escape 'of solvent vapors or gases.

After having been relieved of the solvent 35 I vapors, the work is transferred to a room of somewhat higher temperature, preferably about thirty-two degrees Fahrenheit, where it is subjected-to another period of d ing.

From this stage the work may be passe into a'room of normal. atmospheric temperature and if a greater degree of hardening is required the work may be passed through successive stages ofcuring at lh'gher temperatures. x,

In the curing room advantage is taken of two physical conditions, i. e., the lowering of the temperature causes a lowering of the vapor tension, consequently the atmosphere can contain less water vapor at the lower temperature than at a higher temperature, and advantage isalso taken of the latent heat of evaporation.

Even though the temperature of the curing room he maintained quite low, the evaporation of the solvent nevertheless produces a refrigerating effect tending to lower the temperature of the coated article below that of the surrounding atmosphere and thereby induce on the surface coating condensation of moisture in the form of ice crystals. ."Ihis efl'ect, however, is counteracted by extracting the moisture from the air to a degree well below the saturation point before the air comes into contact 'with the coated article.

To'this end the air entering the curing room is initially cooled to a quite low temperature. This room is maintained ordinarily at subzero Fahrenheit temperature and is prcferably maintained at approximately forty dethe condensation of moisture therefrom in the form of ice or frost, leaving the air com-n paratively dry, yet but little below the point of saturation at the resulting temperature.

The temperature of the air is then slightlf' raised to that of the curing room temperature. By raising the temperature of the curing air approximately five to ten degrees, not only is danger of moisture condensation by the refrigerating effect of the evaporatlng solvent removed, but the capability of the air to absorb the solvent vapors, which have a great afiinity for moisture, is greatly increased. The slight warming of the air after it has been lowered to such temperature as to condense its entrained moisture, so increases its capacity to absorb and retain moisture that none of the small remaining amount of moisture in the airwill be condensed upon thesurface of the work, which, due to the evaporation effect of the solvent, is somewhat colder than the air circulating thereabollt.

' The low temperature retards the evaporation of the solvent, allowing sufiicient time for the solvent to escape from the deposited matcrial without causing pimples or bubbles. The subjection of the coated article to such lowered temperature, also enables a heavier or deeper deposit to be retained upon the article than would otherwise be possible. Thus coverings or coatings of considerable thickness may be effected by a single dipping operation. To afford coverings of maximum thickness, the dipping and curing operations may be repeated several times.

The present material must not become confused with lacquers made from cellulose base, which are variously used and applied in liquid form. Such lacquers, although derived from the same base to which are added various gums and solvents, differ widely from the present material in character, being brittle and dry, lacking the tensile strength and durability. and can be practically applied only in thin coatings, whereas the present ma:'

terial can be applied to form a quite thick casing or shell about the art cle, which will be hard but tough and practically .unbreak able.

Although the commercial material known as pyroxylin, pyroxyle, or pyroxyline,-otherwise known specifically as celluloid, is the preferable material, the invention is not specificallylimited to this material but includes other nitrocellulose derivatives or cellulose ircetate having the characteristics of pyroxy- While the conditioning of the air in the curing room has been described as being cooled to a rather low degree to precipitate the moisture, and the temperature then raised to increase itsvapor carrying capacity before .it reaches the coated article, such air is not necessarily colder than the surface of the coated article with which the circulating air comes in contact. -The evaporation of the solvent produces a refrigerating effect which tends to lower the temperature of the surface below that of the surrounding atmosphere even at the low temperature of the curing room. a r

The various temperatures herein mentioned are given for illustrative purposes only and with no intent to arbitrarily limit this invention to such stated temperatures nor relative temperature ranges. It is to be understood that the temperature and relative variations thereof may be varied within reasonable limits to meet different conditions of use, differences in the material composition and solvent employed, and results desired.

While only a few solvents for nitrocellulose material have been mentioned, and only a few liquids referred to for use as the intermediate setting bath and for extraction of the solvent, it will be understood that other solvents and other bath liquids having the necessarycharacteristics as hereinbefore described may be employed in lieu of those mentioned,

The pyroxylin material or the like may be cured in properly conditioned air alone without the use of the setting and solvent extracting bath. It may also be cured and the solvent extracted by the bath method alone to a point where the article may be exposed to air at atmospheric temperature without harmful effect. However, for practical commercial operation the hereinbefore described combined method of bath treatmentfollowed by low temperature dry air treatment is preferred.

Fromthe above description it will be apparent that there is thus provided a method of the character described possessing the particular features of advantage before enumerated' as desirable, but which obviously' is susceptible of modification in its steps, se-

quence, detail procedure and arrangement of apparatus without departing from the principle involved or sacrificing any of its ad"- vantages.

While in order to comply with the statute the invention has been described in language in any of its forms or modifications within the legitimate and valid scope of the ap--" pended claims.

Having thus described our invention, we claim:

1. The herein described method of coating articles with pyroxylin or the like, consisting in dipping the portion of the article to be coated in a viscous solution of the coat ng material at approximately 7 0 degrees Fahren-' heit, chilling the deposited coating to effect quick setting and preventing distortion of the deposit, extracting from the deposited material a portion of the coating material solvent and evaporating the remaining-solvent in an atmosphere of sub-zero temperature Fahrenheit and of low humidity char--- ing in-dipping the. portion of the article to be coated in a viscous solution of the coating material, submerging the coated portion of the article in a cold bath having a temperature sufiiciently low to cause the coating ma terial to chill and set, and subsequently evaporating the solvent from the deposited material While maintaining the article at a low temperature.

3. The herein described method of coating articles with pyroxylin or the like,,consisting .in dipping the portion of the article to be coated in a viscous solution of the coating material, submerging the coated portion of the article in a bath of material having an affinity for the solvent and having a temperature of approximately Fahrenheit less than that of the solution in which the article has been dipped whereby the material adhering to the article is congealed and a portion of the solvent is extracted from the deposit of coating material and subsequently evaporating from the deposited material the remaining solvent.

4. The herein described method of coating 1 articles with nitrocellulose material consisting in dipping the article into a solution of the coating material, dipping the coatedarticle into a bath of material having an affinity for the solvent and maintained at a temperature sufficiently low to efiecta chilling and setting of the coating material and subsequently curing the coated article in a subzero Fahrenheit temperature.

5. The herein described method of coating articles with pyroxylin or the like consisting in dissolving the m aterial in a solvent to form a viscous liquid, dipping the article to be coated in the viscous liquid at approximately r normal atmospheric temperature, dipping the I coated article in a bath maintained at a ma-' terially lower temperature to set the material,

and subsequently evaporating the remaining solvent in an atmosphere from which moisture hasbeen extracted at a sub-zero Fahrenheit temperature.

6. A method of coating articles with pyroxylin or the like consisting in dissolving the coating material to a viscous liquid, dipping the portionof the article to be coated into such liquid, draining therefrom the surplus material, submerging the coated portion of the article in a hardening and setting bath having a temperature materiallylower than has been dipped whereby the coating material that of the viscous liquid in which the article is congealed thereon, and subsequently evaporating from the coating material any'remaining solvent.

- '7. A method of coating articles with pyroxylinor the like consisting in dissolving the coating material to a viscous liquid, dipping the portion of the article to be coated into such liquid, draining therefrom the surplus material, submerging the coated portion of the article in a body of material having an taine at the temperature materially lower than that of the liquid in which the article has been dipped by which the material is congealed and by which a considerable portion of the solvent is extracted priorto curing, and subsequently curing the coating material at low temperature. 8. A method of coating articles with pyroxylin orthe like consisting in dissolving the coating material to a viscous liquid, dipping the portion of the article to be coated into such liquid, draining therefrom the surplus material,.initially congealing the coating ma-- terial to prevent displacement, extracting from the deposited coating material a considerable portion of the solvent and subsefor the coating material solvent mainquently evaporating the remainder of the solvent "while maintaining the coated article at a temperature materially lower than that of the liquid in which the article-has been dipped.

9. A method of coatingarticles with pyroxylin or the like consisting in dissolving the coating material to a viscous liquid, dipping the portion of-the article tobe coated into such liquid, draining therefrom the surplus material, temporarily submerging the coated article in a bath of petroleum distillate to effect extractionof the solvent and evaporating remaining solvent from the coated article in a sub-zero temperature. i

10. A method of coating articles with pyroxylin or the like consisting in dissolving the coating material to a-viscous liquid, dipping the portion of the article to be coated into such liquid, draining therefrom the sur-- plus material, submerging the coated article in a bath of petroleum distillate maintained at low temperature to set the deposited coating material by simultaneously-chilling the material and extracting the solvent, and subsequently evaporating the-remaining solvent at a sub-zero Fahrenheit temperature. 11. method of coating articles with pyroxylin or the like consisting in dissolving the coating material to a viscous liquid, dipping coated article through successive stages.

In testimony whereof, we have-hereunto set our hands this 26 day of May A. D. 1930. WILLIAM C. HAMPTON,

CHARLES N. GARBER. 

